1. Field of the Invention
The invention relates to a grid of crossing grid bars, in particular, as a wall of a cage for receiving a plastic container in the context of a complete arrangement of a pallet container for storing and/or transporting substances.
2. Description of the Related Art
In conventional grids of this type the grid bars are round iron rods welded together at their crossing points. Grid casings for pallet containers are also known which are comprised of tubular grid bars that are indented at the crossing points and connected by resistance welding.
The grids made of round iron rods are heavy because they require a tight grid pattern to fulfill the static requirements of the substances to be stored/transported.
The grids of tubular rods are more lightweight. However, their manufacture of tubular rods is cumbersome insofar as the indentations must be produced in a separate working step at preset locations and the grid rods then can be used only in the thus predetermined manner.
It is an object of the present invention to provide a grid which is as light as possible for preset static requirements set by the substances to be stored/transported and which does not require preparations of the crossing locations at the grid bars.
In accordance with the present invention, this is achieved in that the first grid bars extending in one direction are comprised of an open profile having two outwardly bent-away borders extending in a common plane, in that the second grid bars extending in the other direction are also comprised of such profiles or of a closed profile that has at least one planar profile wall, and in that the first and second grid bars are positioned relative to one another such that the bent-away borders rest against one another or that the bent-away borders of the first grid bars rest against the aforementioned planar profile wall of the second grid bars and are connected to one another at the contact surfaces.
This grid is even lighter than the known grids of tubular grid bars for the same strength, because the tubular rods overall require a greater material cross-section as a result of the weakening at the indentation locations. The welding of the absolutely planar surfaces at the crossing points of the inventive grid is more controlled than at the indentations; instead of spot welding it is also possible to employ projection welding and, in principle, also resistance welding. Moreover, the open profile can be shaped of steel strip which can be easily galvanized completely, in contrast to the tubes which always have an interior that is not galvanized.
In comparison to the grids of round iron rods, in addition to the weight savings, there is also the advantage of a substantially reduced number of crossing points which must be welded.
Instead of welding, or in addition thereto, it is in principal also possible to provide at the bent-away borders a connection by stamping and/or punching.
In applications in which a greater torsional stiffness or buckling resistance is required, an open profile should be used for the grid bars extending in the one direction and a closed profile should be used for the grid bars extending in the other direction.
The open profile is provided with the bent-away borders, for example, at a profiled portion of a substantially square cross-section.
For use in a pallet container it could be preferred to have an embodiment in which the open profile has the bent-away borders provided at a profiled portion which adjacent to the bent-away borders has a rectangular cross-sectional part and adjacent thereto a trapezoidal cross-sectional part. The pallet containers can slide away from one another at the trapezoidal cross-sections when the careless positioning next to one another causes entanglement of the grid casings.
If it is desired to increase the strength or to reduce the possibilities of accidents, the bent-away borders can be folded over at the border edges.
The profile is thus stiffened and the border edges are rounded, a larger radius being produced at the same time.
In a further embodiment, the grid is provided at its borders with a surrounding profile.
This provides, on the one hand, increased strength as well as, on the other hand, increased safety. This measure is especially expedient at the top and bottom borders of a grid with vertical grid bars of an open profile: An open bent-away sheet metal profile is no longer buckle-resistant at ends not secured by a surrounding profile, and, moreover, the corners present a risk for injury.
Two variants of the surrounding profile are disclosed here in more detail:
In one embodiment a substantially U-shaped, preferably elongate rectangular, profile is provided and the surrounded ends of the grid bars are connected by welding and/or by stamping and/or by punching at least with their bent-away borders to one leg of the U-shaped profile, preferably also at the opposite side to the other leg of the U-shaped profile.
In the other embodiment it is suggested that the ends of the grid bars are pressed flat, that the surrounding profile rests with two parallel edges against the grid bar ends and is welded and/or connected by stamping and/or connected by punching to at least one flat side, preferably both flat sides, of the flat-pressed grid bars.
In the vertical positioning of the grid, which will be used in most applications, the U-shaped profile should generally be the most expedient for the bottom border. The vertical grid bars remain thus more stable in comparison to flat-pressed ends and the U-shaped profile provides various support and connecting possibilities. It can then be placed with its usually planar underside onto feet or other supports. The top edges of the sidewalls of the U-shaped profile, which are generally also planar, can serve as a support and connection to other components. With the especially suggested use of the grid in a pallet container they serve as a support and connection to the bottom.
The other surrounding profile for flat-pressed grid bar ends appears to be expedient in most cases for the top border of the grid. It can be round, or at least rounded, and is thus suitable for manual gripping and manipulation, which is occasionally necessary at the top border of, for example, a grid cage. In the especially suggested use of the grid in a pallet container, the profile and its connection to flat-pressed grid bar ends, on the other hand, provides enough strength to place a further pallet container on top.